1. Field of the Invention
The present invention relates to an antenna switch and a method of providing a radio frequency signal to an antenna switch.
2. Description of the Related Art
In transceivers, such as mobile telephones, it is known to provide an antenna switch for switching between the transmit and receive path to the antenna. Indeed, multi-band and/or multi-mode devices are known having two or more transmit paths and/or two or more receive paths. Antenna switches may be provided to switch between these parts.
Each transmit path requires a power amplifier to amplify a radio frequency signal to a high enough level for it to reach a receiver, such as a base-station. For multi-mode and multi-band devices, separate power amplifiers may be needed for each mode or band.
FIG. 1 of the accompanying drawings illustrates schematically an example of an arrangement of power amplifiers and a switch for a dual band transceiver. The switch 10 includes transmit connections 12 and 14 for inputting respectively GSM 900 and GSM 1800 radio frequency signals. It also includes received connections 16 and 18 for outputting GSM 900 and GSM 1800 radio frequency signals, together with an antenna connection 20 for connection to an antenna.
The illustrated power amplifier for the transmit (TX) paths has three stages, though two or four stages could be used depending on the application. As illustrated, the first stage 22 and second stage 24 can be provided in common for both transmit paths. However, it is usually necessary, as illustrated, to provide separate third stage amplifiers 26, 28 for the respective transmit paths. It will be appreciated also that each subsequent stage of amplification requires greater die area than the previous stage. The areas required for the final stage of amplification are significantly great and, hence, add to the size and cost of producing the arrangement of FIG. 1 for multi-band and/or multi-mode devices.